This invention relates to a hydraulic torque impulse generator, primarily but not exlusively intended for screw joint tightening applications, such as power wrenches.
In particular, the invention concerns a hydraulic torque impulse generator comprising a drive member coupled to a rotation motor, a fluid chamber in said drive member, and an output spindle extending into said fluid chamber, and seal means associated with said drive member and said output spindle and arranged to sealingly divide during certain repeated intervals of the relative rotation of said drive member and said output spindle said fluid chamber into at least two high pressure compartments and at least two low pressure compartments.
An impulse generator of the above type is previously described in U.S. Pat. No. 4,553,948. In this known device the seal means comprises two sets of axially extending seal ribs which are asymmetrically disposed in relation to a diameter line in order to obtain a sealing cooperation between the seal ribs just once every relative revolution between the drive member and the output spindle.
The specific seal rib arrangement of this known device is disadvantageous in that the bypass flow across the seal ribs during the non-sealing sequences is restricted to some extent, which means a slower acceleration of the drive member and a lower impulse energy output.
The above problem is solved by the torque impulse generator according to the invention.
A preferred embodiment of the invention is hereinbelow described in detail with reference to the accompanying drawing.